Special thanks to BRIKEL94SL and My92Stealth. Both offered their cars as subjects for me to photograph.
This thread explains the vacuum hose reduction for the 1G Federal (’91-93, 1G California (’91-93), and 2G Hybrid ECU (’94-95) cars. Below are brief descriptions of the systems involved, a list of tools required to perform the modification, and step-by-step instructions for the modification itself. It is intended to be a general guide only; hose reductions will vary according to individual setups and preferences.
Throughout the writeup I will refer to sources of boost pressure and vacuum. Vaccum conditions exist only after the throttle body. Boost pressure conditions exist only after the turbochargers. Pressure before the turbochargers is 0 gauge or 14.7psi at sea level (ASL).
I am assuming that readers have reviewed at least the Technical Information Manual on
www.stealth316.com, if not the service manual’s explanations of the systems below. I am also assuming that readers have seen and can interpret that hose routing diagram from the Service Manual (
http://www.3si.org/forum/attachment....chmentid=59639), and that they understand the basic function of a turbocharger wastegate. What follows is a quick reference only.
Systems removed:
Exhaust gas recirculation (EGR) solenoid and lines
Evaporative emissions (EVAP) solenoid, valve, canister, and lines
Boost control solenoid (BCS) and lines
Fuel pressure regulator solenoid (FPRS) and lines
Tools needed (in order of importance):
Knife
Philips and flathead screwdrivers
3/8 ratchet and socket set (the usual 10mm and 12mm)
Pliers—needlenose, conventional, and the snipping type
Materials needed:
4mm vacuum line
6mm vacuum line
Assorted plastic or brass vacuum tees
Vacuum caps
RTV sealant
Remove the following parts in preparation:
Battery
Y-pipe
Front and rear turbo intake pipes
Air filter, MAS, BOV, and intake splitter
Coolant overflow tank (remove the bolts, raise the tank, and rest it on the headlight bucket)
[NOTE: It is possible to do the hose reduction without removing some of these things, but it is easiest with them removed.]
Part 1: Deleting the unnecessary parts
When you begin, you'll be looking at a nest of vacuum lines and a hardline bundle on the firewall.
Brian had already removed a few of his lines, but here you can see the hardline bundle and the solenoid rack
An alternate view.
Begin the hose reduction by cutting all the vacuum lines running from the hardline bundle on the throttle body (TB) to the solenoid rack on the firewall. Cut the vacuum lines running from the plenum to the H-connector, BCS, and rear wastegate (WG). Cut the vacuum lines running to the EGR valve. Cut the vacuum lines running to the small bundle of hardlines beneath and to the passenger side of the EGR also. (These hard lines connect the BCS and EVAP solenoid to the front wastegate and the EVAP valve respectively. See below for further explanation.)
Remove the two upper bolts on the TB. Cut or disconnect the 3 lines running from the hardline bundle to the TB nipples. Remove and discard the hardline bundle. Reinstall the TB bolts.
(photos to come)
Remove the 3 10mm bolts securing the solenoid rack to the firewall. Disconnect the main electrical connector powering all the solenoids. Remove the solenoid rack.
At this point there should be no vacuum line remaining in the area of the engine bay between the firewall and the TB/plenum. Move towards the front of the engine bay so that you can remove the EVAP and valve.
Near the front WG actuator and beneath the PTU are hoses coming off of a 4-line hardline bundle. One goes to the front WG actuator; the rest go to the EVAP canister. Cut these.
Remove the EVAP canister by undoing the band clamp. The EVAP canister is held to the frame rail by a metal band that uses a clasp similar to a mason jar or a ski boot. Because there are some assorted brackets and lines holding the canister itself to the bracket, the best way to remove it is to violently mangle it until it submits. Save the
black plastic valve.
Further, during removal it is necessary to cut the vacuum hose connecting the canister to the hardline running from the fuel tank to the engine bay (see my quick reference above). The hardline runs along the frame rail (under the MAS), then makes a quick downward turn. It is visible in the upper right hand corner of this photo of the EVAP canister.
The final thing to remove is the 4-line hardline bundle mentioned just earlier. These are often a source of confusion for people doing the hose reductions. People are tempted to cap or connect them. All they do is connect the EVAP solenoid and BC lines to the EVAP canister and the front WG. Because the hose reduction removes the solenoids and the stock BC lines, this hardline bundle connects nothing to nothing.
The bundle runs the alongside the engine, beginning beneath the EGR valve, turning down under the throttle body, under the thermostat housing, under the coil packs, and terminating about 3 inches away from the front WG actuator diaphragm.
It will require some yanking and bending to remove. Do not expect it to slide out instantly.
Clint